1. Field of the Invention
The present invention relates to a vacuum pump in which a rotor is supported by a lubricated ball bearing.
2. Description of the Related Art
In a vacuum pump in which a ball bearing is used as a bearing for supporting a rotor, lubrication of the ball bearing comes to an issue. In a dry vacuum pump described in Japanese Unexamined Patent Publication No. 2002-317790, a labyrinth seal is provided between a space in which a motor and a ball bearing are arranged and a pump exhaust port side. With such a configuration, a reverse flow of oil vapor to an intake port side is prevented.
The invention described in Japanese Unexamined Patent Publication No. 62-288386 is a vacuum pump in which a lower part of a rotating body is supported by a spherical spiral groove bearing, and a lip seal plate is provided for a rotor shaft, so that oil and oil vapor are prevented from leaking out to an exterior of an oil container.
However, in a case of the configuration described in Japanese Unexamined Patent Publication No. 2002-317790, the oil vapor goes over the entire arrangement space of the motor and the bearing. Therefore, when a pressure is changed on the pump exhaust port side, a gas flows into the arrangement space or the gas flows out from the arrangement space via the labyrinth seal, and in accordance with the flow-out of the gas, the oil vapor of the arrangement space also flows out. As a result, oil used as a lubricant of the bearing (base oil in a case of grease lubrication) is decreased, so that the life of the lubricant is deteriorated.
In a case where the lip seal plate described in Japanese Unexamined Patent Publication No. 62-288386 is used, in order to make the lip seal plate bearable for high-speed rotation, there is a need for forming an oil film of lubricating oil in apart where the lip seal plate and the rotor shaft are in contact with each other. Therefore, this structure cannot be applied to a ball bearing of grease lubrication.